1. Field of the Invention.
The present invention relates generally to apparatus and methods for determining the dullness of cutting tools used in metal machining operations. In particular, the present invention is a method for determining cutting tool dullness as a function of cutting tool-caused changes in properties of the machined surface.
2. Description of the Prior Art.
In both automatic and manual machining operations it is important to know the degree of wear or dullness of the cutting tool. Since cutting tools are expensive, and productivity is lost while they are being replaced, it is desirable to use the tool as long as possible. On the other hand, dull cutting tools result in inefficient machining operations and workpieces which do not meet required specifications.
Quite a few different methods for monitoring cutting tool dullness are currently used. These methods are disclosed in articles entitled, "Measuring Cutting Tool Wear On-Line: Some Practical Considerations", Manufacturing Engineering, July 1984, pages 55-60; and "New Tool-Wear Sensors Aid Adaptive Machining", Tooling and Precision, December 1987, pages 41-43. The methods disclosed in these articles are characterized as being either direct or indirect methods. Indirect methods include force measurement, temperature measurement, vibration measurement, and sound measurement techniques. Direct methods use workpiece size change, radiometric, tool/work junction electrical resistance, and optical monitoring.
In view of the large number of methods currently used to diagnose cutting tool dullness, it is evident that none of them have the qualities needed for all situations. There is, therefore, a continuing need for new methods for monitoring cutting tool wear. To be useful the method must be quick, accurate and reliable.